Electric fuse



ELECTRIC FUSE Filed Aug. 6

1 lll will l Patented June 1, 1954 ELECTRIC FUSE Paul C. Hitchcock,

Mass.,

Lawrence, Mass., assignor to The Chase-Shawmut Company,

Newburyport,

a, corporation of Massachusetts Application August 6, 1951, Serial No. 240,553 13 Claims. (CI. ZOO-432) This invention relates generally to protective devices for interrupting faulted electric circuits, and more particularly to fuses.

One object of this invention is to provide a highly elTective one time fuse which is less expensive to manufacture than comparable one time fuses which were known heretofore.

Another object of this invention is to provide a fuse wherein conductively connecting the fuse link to the terminal caps involves a minimum of labor.

Another object of this invention is to provide a fuse wherein the fuse link is held in position by crimping of the terminal caps or ferrules of the fuse.

Still another object of the invention is to provide a fuse wherein the conductive connections between the fuse link and the terminal caps consist of spot Welds and are situated at readily accessible points outside of the casing of the fuse and outside of the terminal caps or ferrules of the fuse.

Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

For a better understanding of this invention reference may be had to the accompanying drawing in which Fig. l is a View, partly in longitudinal section, of a fuse structure embodying this invention;

Fig. 2 is an end view of the structure shown in Fig. l upon removal of one of the terminal caps or ferrules;

Fig. 3 is a view, partly in longitudinal section, of a fuse structure similar to that shown in Fig. l but involving the use of a pair of fuse links rather than but one single fuse link only;

Fig. 4 is an end View of the structure shown in Fig. 3 upon removal of one of the terminal caps or ferrules;

Fig. 5 is a view, partly in longitudinal section, cf another multi-link fuse embodying this invention;

Fig. 6 is a left end view of the structure shown in Fig. 5 upon removal of the left terminal cap or ferrule of the fuse;

Fig. 7 is a right end view of the structure shown in Fig. 5 upon removal of the right terminal cap or ferrule of the fuse;

Fig. 8 is a View, partly in longitudinal section, of still another embodiment of this invention wherein the inse link is arranged in coaxial relation with respect to the casing of the fuse;

Fig. 9 is a side elevation of a part of the structure of Fig. 8, i. e. ci the fuse link proper and of the elements associated therewith seen from the Wide side or" the link rather than the edge side thereof;

Fig. l0 is an end View of the structure shown in Fig. 9; and

Fig. ll is a View, partly in longitudinal section, showing one end portion of yet another embodiment of this invention wherein an insulating disk intervenes between the terminal elements of the fuse link and the adjacent end wall of a terminal cap.

The saine reference signs are used in all the iigures to designate like parts.

Referring now to Figs. 1 and 2, the reference numeral I' has been applied to a fuse casing con sisting of one single tubular element of insulating material having an external cylindrical surface at both ends thereof. This casing may be made of paper board to limit the cost of the fuse provided that the pressure developed Within casing i during the interrupting process is kept sufilciently small so as not to exceed the very limited mechanical strength of a paper board casing. Fuse link 2 is of the ribbon type and extends substantially in the direction of a diagcnal of a longitudinal cross-section of casing l. Link 2 is provided with a plurality of spaced holes 2a whereby a plurality of zones of restricted cross-section is produced of which each consists of a pair of parallel current paths. This configuration of the link 2 tends to greatly increase the interrupting capacity of the fuse structure. A rivet 3 made of suitable metal is inserted in one of the holes 2a of link 2. Rivet 3 is made of a metal tending to form at a predetermined temperature an alloy with the metal of which fuse link 2 is made having a lovver fusing point than the metal of Which fuse link 2 is made. On account of this feature the fuse Will blovv at protracted srnall overloads before reaching an undesirably or dangerously high temperature. Ribbon type link 2 may consist, for instance, of tin platedcopper and rivet 3 may consist of tin. Fuse link 2 is provided with terminal elements 2 and 2 w ch form integral parts of the fuse link. Terminal elements 2 and E" consist preferably of the outer ends of the link ribbon 2, i. e. the fuse link 2 proper and the terminal elements 2 and E thereof may be unitary. In other instances of which an example is shown in Figs. 8 to lo, inclusive, an integrated composite link-terniinal-element-structure may take the place of the above described unitary link-terminal-element-structure. In such a composite structure the link 2 proper and the terminal elements 2' and 2" thereof may consist of different metals joined together by appropriate means as, for instance, spot-welding. As shown in Figs. l and 2, the terminal elements 2 and 2" are bent or folded around the edges i and i of casing I, and overlap the outer surface Ia thereof. Casing I is closed by a pair of ter minal caps or ferrules l' and d", preferably made of brass, of which each is arranged at, and closes, one end of casing I. Caps Il' and 5:1" clamp terminal elements 2' and 2 0f the fuse link 2, respectively, between the outer surface Ia of casing I and the inner surfaces fia and 4a oi caps Il and 4". The edges Ib and 4b of ferrules I' and II" remote from the edges or rims I and I of casing I are crimped, thus holding both caps 4 and and link 2 and its terminals 2' and 2" rmly in position. Terminal elements 2' and 2 are folded or lapped about the edges Ib and 4"b of terminal caps 4i and 4" and spot welded at .5 and 5" to the outer surfaces Ic and Ll"c of caps Il and 4". The areas or points where Contact is established by spot-welding between terminal caps il and d and terminal elements 2 and 2 are situated immediately adjacent edges Ab and #Wb on the outer surfaces Il'c and 4"c of caps i and d". These areas or points are readily accessible by the spot-welding electrode upon complete assembly of the fuse.

The inside of casing I is filled with a pulverulent arc-quenching nller 6 which may be quartz sand, gypsum or any other suitable ller material.

Referring now to Figs. 3 and 4, the structure shown therein is designed to carry and to interrupt relatively higher currents requiring the use of two fuse links 2 connected in parallel rather than merely one. The two fuse links 2 are arranged in substantially parallel planes as shown in Fig. 4. The two fuse links 2 are each provided with a rivet 3 of tin to initiate fusion by alloy-formation at small protracted overloads.

Each of the two fuse links 2 has a pair of ter- 1 minal elements 2 and 2" and each of the two fuse links 2 extends substantially in the direction of a different diagonal of a longitudinal cross-section of casing I, as clearly shown in Fig. 3. Each pair of terminal elements 2 and 2" of each fuse link 2 is folded about one of the two rims I and I" of casing I overlapping the outer surface Ia thereof. A.' pulverulent arcquenching filler within casing I surrounds, and is in intimate contact with, the pair of fuse links 2. Each of the pair of terminal caps 4 and 4" closes one end of casing l. Blade contact 'i' forms an integral part of cap il and blade contact I forms an integral part of cap 4". Blade contacts 'I' and 'I" are intended to cooperate with the contacts in a fuse holder not shown. Each pair of terminal elements 2' and 2" of each of said pair of fuse links 2 is also folded about edges 4'b and "b of terminal caps ib and Vb of terminal caps d. and Il remote from rims i' and I. Spot-welds 5 and 5" outside of casing I and outside of terminal caps Ll and A" conductively connect each of the terminal elements 2 and 2" to one of the terminal caps 4' and 4, respectively.

Referring now to Figs. `5 to 7, inclusive, the tubular casing I is made of insulation material such as paper or liber and has a circular crosssection. A plurality as, for instance, three, fuse links 2 is arranged within casing I and each fuse 4 link 2 has a pair of terminal elements 2' and 2" forming an integral part of the link 2. Each fuse link 2 is arranged along a generatrix of a truncated cone and angularly displaced with respect to all the others of said plurality of fuse links. The above angular displacement is degrees if three fuse links are used, as shown in Figs. 5 to 7, and would be 90 degrees in case four instead of three links were used. The diverging terminal elements 2 on links 2 are folded around rim I' of casing I and extend along the outer surface Ia thereof. An insulating disc 3 having an aperture 8a at the center thereof is arranged adjacent to rim I" of casing I. The converging terminal elements 2" of the three fuse links 2 pass through aperture 8a in disc 8 and are folded around rim I of casing I and extend along the outer surface Ia thereof. A pulverulent arc-quenching filler E is arranged in casing I in intimate Contact with the three links 2. The two terminal caps Il' and il of which each is provided with a blade contact l and respectively, close the two ends of casing I. Each of the terminal elements 2 and 2 of each fuse link is lapped around edges d'0, and i'b of caps il and II" remote from rims I and i of casing I. Spot-welds 5' and 5" outside oi casing I and outside of caps d' and il" conductively connect each of the pairs of terminal elements 2' and 2 to one of the terminal caps il' and d.

As shown in Figs. 5 and 6 links 2 are preferably provided with a series of equidistant circular perforations Za arranged along the longitudinal axis of the respective link. If the fuse is desired for the interruption of protracted small overn loads in addition to the interruption of shortcircuits, a tin rivet 3 may be tted in one of the above referred-to holes of each link. Preferably tin rivets 3 are ntted into off-center holes.

Referring now to Figs. 8 to l0, inclusive, reference numeral 9 has been applied to a thermally responsive switching device which is built into the fuse, i. e. accommodated in the casing I thereof. Such built-in thermally responsive switching devices which comprise generally a pair of cooperating contacts spring biased to contact open position and normally held in closed position by solder, preferably an eutectic alloy, are well known in the art and, therefore, need not be described in detail. The preferred form of built-in thermally responsive switching devices is fully disclosed in United States Patent No. 2,321,711 to Elmer H. Taylor, Fusible Electric Protective Device, June l5, 1943, assigned to the same assignee as the present invention. Switching device 9 could be replaced, if desired, by any other thermal circuit interrupting means predicated upon formation of a circuit interrupting gap at the occurrence of small protracted overloads.

The switching device or thermal interrupting means 9 is supported at each side thereof by a portion of a fuse link 2. Fuse link 2 is provided with necks or portions of restricted cross-section 2b where the rate of heat generation is relatively high. The heat there generated is conducted to the heat-responsive switching device S and causes operation thereof on the occurrence of fault currents of small magnitude but inadmissible duration. The two portions of link 2 by which device 9 is supported are arranged within an arc-quenching filler 8. This filler rapidly quenches the four series arcs formed at the necks 2b at the occurrence of fault currents of short-circuit current proportions. A plurality of terminal elements 2a and 2'b is associated with the left end of link 2. Similarly, aplurality of terminal ciments 2"a and 2b is associated with the right end of linl: 2.

In the embodiment or" the invention shown in 0 Figs. 8 te i0, inclusive, but tivo terminal ele-- ments are associated with each end of the link 2, out the number of such terminal elements might ce increased Where mechanical strength requirements or current carrying requirements so ictate.

Each of the plurality of terminal elements 2o, 25 and 2a, 2li, respectively, fornis integral part of the link 2 by loeingr spot Welded at points lil' and It" or in any other suitable manner secured to it. r"'errninal elements 2a and Eb are folded around edge or rim l of casing l. Terminal elements 2a and 2"b are folded around edge 0r riin l of casing I. The terminal caps 4 and d of which each is provided with a clade contact i clamp the terminal elements 2'a, 2b, 2a and 2WD firmly Toets/een the inner surfaces 'a and ci caps el and the outer surface lo of casing i.

It will ce noted that inse link i. in the structure according to 8 is arranged in coaxial relation with res` ec to casing i wheres in all other embodiments of the invention the position of the axis of the use link 2 or fuse links 2 is different from the position of the axis of the casing i.

The terminal elements Za, 2'b and 2@1., 2*19, respectively, associated with the same end of fuse linlr; 2 are angularly displaced about le() degrees. The ends of the terminal elements 2a. b, two, 2"Zo which project beyond the axially inner rims of caps 4 and 4 are upturned and spot Welded at 5 and 5 to cap 4 and respectively.

The structure shown in Figs. 8 to 10, is a considerable improvement over the structure shown in the above Taylor patent with regard to cost of manufacture as Well as with regard to dimennal stability.

Jnder soin-e conditions, it will be found desirable to employ a structure in which the portions of terminal elements of the fuse link '-.vlilcn are folded about edges of the casing do not come in contact with the adjacent end Walls of the terminal This may be accomplished i. various ways such as by forming a notch in end of t c casing Wall and folding the terrr-.inal about the bottom edge of the notch, in aced rela en to the adjacent end Wall of the f i d. A comparable result is "3 ding a suitable insulating disk rrnnal cap for intervening between erminal element and the end wall of the terminal cap, as illustrated at 2 in Fig. 1l. 60

Devices i accordance with the invenn may have their oasings entirely lled with pulverulent aro-quenching ller as shown in Wnerein the ller surrounds the l, or the c d with nu :own in Fig. 1in casing i sometimes a substantial space 6a l is left Without iiller E therein. vl'l he found desirable, especially .en fuses embodying the invention are to inupt D. C. currents, to relieve the oasings l of severe interi y generated pressures by providing substan interior space Se, as in Fig. 5, for expansion of gases generated when a fuse operates. Casings I filled with pulverulent arcquenching nller 5 to approximately 80% of their capacity, still effectively interrupt A. C. and D. C faalt currents of short-circuit proportions and of moderate overload proportions.

Having disclosed several preferred embodiments of the invention, it is desired that the same be not linited to the parti ilar structure disclosed. It will be obvious to any person skilled in the art that ina-ny modiiications and changes ni y be made without departing from the broad spirit or scope of tlie invention. Therefore it is detliat s" invention he interpreted as broadly as possible and that it loe limited only as required by the prior state of the art.

I claim as rny invention:

l. A one time fuse comprising a casing or insulating material, a pulver lent arc quenching min said casing, a fuse link of a high fusing point metal arranged Within said casing and surrounded by said nller, terminal elements forron ing integre-.l parts of said fuse linlr, said fuse link being arranged in spaced relation with respect to the inner Wall of said casing except for said terminal elements, terminal elements being bent about the cages of said casing and overlap1 ping the outer surface tn coi terininal caps eX- tending over the portions of said terminal elements overlacning said outer surface of said casing and cr eed at the juxtaposed edge zones eef, said terminal elements being also bent contact said terminal caps at points situated outc surfaces thereof, and spot-weide coniveiy connecting said terminal elements and terminal caps at said points.

2. A one time fuse comprising casing ing oi on single tubular ele nt ci in material leaving an external cylindrical su t both ends thereof, a pulver-dient quen: nin said casing, fuse link of a li gli ,ooint metal arranged within said cas rounded cy sai-'i filler, terminal elements of i1 fusing point metal forming in of said fuse link bent about tlie casing upon said external cylio thereof, terminal caps for closing said terminal caps having cyiindi surfaces engaging said external ey face or" said casing and being criiroefi relative movement between said linal elements and. said termin il terminal elements being also lient axially inner edges of terminal spot-welded to tlie outersur"aces reo. immediately adjacent said edges.

3. A one fuse comprising Sistine of one single tubular elerncn ing material having an eiirei'nfl cfflin i face at botn en@q t` c quenching filler 1 l point and having `ends thereof and extending said external cylindrical surface, for closing said casing cri psd inn r edge zones of said terminal linl; being also bent about 'the a.i .y of terminal caps and entendre wardly along the outer sur spot-Welded to saidv outer surface.

4. A fuse compri ng a casing o' material, a .fuse link arranged vfit ing, terminal elements forming in l said fuse link, fuse link being' spaced relation with respect to to offro] nel.

of said casing except for said terminal elements, said terminal elements being bent about edges of said casing and overlapping the outer surface thereof, terminal caps each having an end Wall and a flange and said flanges extending over the portions of said terminal elements overlapping said outer surface of said casing, each said terminal element at a location where it is bent about an edge of said casing being out of Contact with the said end Wall of the terminal cap whose flange extends over its said overlap ping portion, and spot-Welds conductively connecting said terminal elements to outer surfaces of said anges of the terminal caps at the axially inner edge portions of said flanges.

5. A one time fuse comprising a tubular casing of insulating material, a pulverulent arc quenching filler Within said casing, terminal caps for closing said casing, a ribbon-type fuse link a high melting point metal arranged within said casing, ribbon-type terminal elements forming integral parts of said fuse link, said fuse link being arranged in spaced relation with respect to the inn ner Wall of said casing except for said terminal elements, said terminal elements being folded about the circular edges of said casing and overlapping the outer surfaces thereof, said terminal elements being also folded about circular edges of said terminal caps remote from said circular edges of said casing and spot-welded to the outer surface of said terminal caps at points situated immediately adjacent said circular edges of said terminal caps.

6. A one time fuse comprising a casing of insulating material, a pulverulent are quenching filler Within said casing, a ribbon-type fuse link of a high melting point metal with the ends thereof folded about the edges of said casing arranged Within said casing and surrounded by said filler, said fuse link being spaced from the inner wall of said casing except for said fold ends of said fuse link, and terminal caps for closing the ends of said casing, said folded ends of said fuse link being also folded about edges of said terminal caps and spot-welded thereon at the edge zone of the outer surface thereof.

'2. A one time fuse comprising a casing made of insulating material and having a circular cross-section, a fuse link made of a high fusing point metal arranged Within said casing, the ends of said link being folded about the circular rims of said casing at points of said rims displaced about 180 degrees and overlapping the outer surface of said casing, a pulverulent arc-quenching filler Within said casing surrounding said link, terminal caps for closing said casing crimped at the juxtaposed edge Zones thereof, and spot- Welds on the outside of said terminal caps for conductively connecting said folded ends of said link and said terminal caps,

8. A one time fuse comprising a casing of insulating material, a pulverulent arc-quenching filler Within said casing, a fuse link made of high fusing point metal Within said casing and surn rounded by said filler, a terminal element forming an integral part of said fuse link, said terminal element being folded about the rim of said casing and overlapping the outer surface thereof, a terminal cap for closing said casing, said terminal element being also folded about an edge of said terminal cap remote from rim of said casing, and a Weld arranged outside of said casing and outside of said terminal cap for conductively connecting said terminal. element and said terminal cap.

9. A fuse comprising a casing made of insulating material and having a circular cross-section, a pair of fuse links arranged Within said casing in substantially parallel planes, each of said pair f fuse links having a pair of terminal elements forming an integral part thereof and each of said pair of fuse links extending substantially in the direction of a different diagonal of a longitudinal cross-section of said casing, each of said pairs of terminal elements of each of said pair of fuse links being folded about one of the circular rims of said casing and overlapping the outer surface thereof, a pulverulent arc-quenching filler within said casing surrounding said pair of fuse links, a pair of terminal caps each for closing one end of said casing, one of said pair of terminal elements of each of said pair of fuse links being also folded about edges of said pair of terminal caps remote from said rims of said casing,

spot-weide outside of said casing and outside of each of said pair of terminal caps for conductively connecting each of said pair of terminal elements of each of said pair of fuse links one of said pair of terminal caps.

ld. A fuse comprising a casing made of inaulating material and having a circular crosssection, a plurality of fuse links arranged Within casing each having a pair of terminal elements forming an integral part thereof, each of plurality of fuse links being angularly displaced with respect to all the others of said plurality of fuse links and each of said plurality cf fuse links converging toward one end of said casing and diverging at the other end thereof,

r each of said pair of terminal elements of each of said plurality of fuse links being folded about one of the circular rims of said casing and eX- tending along the outer surface thereof, a pulverulent arc-quenching filler Within said casing surrounding said plurality of fuse links, a pair of terminal caps each for closing one end of said casing, each of said pair of terminal elements of each of said plurality of fuse links being also folded about edges of said pair of terminal caps remote from said rims of said casing, and, spot-Welds outside of said casing and outside of each said pair of terminal caps for conductively connecting each of said pair of terminal elements of each of said plurality of fuse links to one of said pair of terminal caps.

ll. A fuse comprising a casing made of insulating material and having a circular crosssection, a plurality of fuse links arranged within said casing each having a pair of terminal elements forming an integral part thereof, each of said plurality of fuse links being arranged along one generatrix of a truncated cone and angularly displaced with respect to all the others of said plurality of fuse links, the diverging terminal elements on each of said plurality of fuse links being folded around one of the circular rims of said casing and extending along the outer surface thereof, an insulating disc having an aperture at the center thereof arranged acljacent the other of said circular rims of said casing, the converging terminal elements of each of said plurality of fuse links passing through said aperture in said insulating disc and being folded around said other of said circular rims of said casing and extending along the outer surface thereof, a pulverulent arc-quenching ller within said casing in contact with said plurality of fuse links, a pair of terminal caps each for closing one end of said casing, each of said pair of terminal elements of each of said plurality of fuse links being lapped around edges of Said pair of terminal caps remote from said circular rims of said casing, and spot-Welds outside of said casing and outside of each said pair of terminal caps for conductively connecting each of said pair of terminal elements of each of said plurality of fuse links to one of said pair of terminal caps.

l2. A fuse comprising a casing of insulating material, a fuse link arranged within said casing, a plurality of terminal elements associated with each end of said fuse link and forming integral parts thereof, each of said plurality of terminal elements being folded around one of the edges of said casing, a pair of terminal caps for closing said casing and for clamping each of said plurality of terminal elements between the outer surface of said casing and the inner surface of one of said pair of terminal caps, each of said plurality of terminal elements being also folded around one of the axially inner edges of one of said pair of terminal caps, and spotwelds on the outer surface of each of said pair of terminal caps conductively connecting each of said plurality of terminal elements to one of said pair of terminal caps.

13. A fuse comprising a casing of insulating material having a circular cross-section, a fuse link arranged Within said casing, a plurality of terminal elements associated with each end ef said fuse link and forming an integral part thereof, said fuse link being arranged in substantially coaxial relation with respect to said casing and each of said plurality of terminal elements being angularly displaced about 180 degrees and bent about the circular rim of said casing immedaitely adjacent thereto and overlapping the outer surface of said casing, and terminal caps lor closing said easingr in metallic contact with said terminal elements at the outer sai@L casing, the area of Contact between said terminal caps and said terminal elements including points situated at the outer surface of said terminal caps.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,090,220 Moor Aug. 17, 1937 2,142,991 Bennett Jan. l0, 1939 2,220,058 Klein Oct. 29, 1940 FOREIGN PATENTS Number Country Date 450,343 Germany Oct. 6, 1927 

